/* SPDX-License-Identifier: SunMicrosystems */
/* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. */
/* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. */

#include "../../common/tools.h"
#include "gammaf.h"
#include "trigf.h"

static const float
two23 =  8.3886080000e+06f, /* 0x4b000000 */
half  =  5.0000000000e-01f, /* 0x3f000000 */
one   =  1.0000000000e+00f, /* 0x3f800000 */
pi    =  3.1415927410e+00f, /* 0x40490fdb */
a0    =  7.7215664089e-02f, /* 0x3d9e233f */
a1    =  3.2246702909e-01f, /* 0x3ea51a66 */
a2    =  6.7352302372e-02f, /* 0x3d89f001 */
a3    =  2.0580807701e-02f, /* 0x3ca89915 */
a4    =  7.3855509982e-03f, /* 0x3bf2027e */
a5    =  2.8905137442e-03f, /* 0x3b3d6ec6 */
a6    =  1.1927076848e-03f, /* 0x3a9c54a1 */
a7    =  5.1006977446e-04f, /* 0x3a05b634 */
a8    =  2.2086278477e-04f, /* 0x39679767 */
a9    =  1.0801156895e-04f, /* 0x38e28445 */
a10   =  2.5214456400e-05f, /* 0x37d383a2 */
a11   =  4.4864096708e-05f, /* 0x383c2c75 */
tc    =  1.4616321325e+00f, /* 0x3fbb16c3 */
tf    = -1.2148628384e-01f, /* 0xbdf8cdcd */
/* tt = -(tail of tf) */
tt    =  6.6971006518e-09f, /* 0x31e61c52 */
t0    =  4.8383611441e-01f, /* 0x3ef7b95e */
t1    = -1.4758771658e-01f, /* 0xbe17213c */
t2    =  6.4624942839e-02f, /* 0x3d845a15 */
t3    = -3.2788541168e-02f, /* 0xbd064d47 */
t4    =  1.7970675603e-02f, /* 0x3c93373d */
t5    = -1.0314224288e-02f, /* 0xbc28fcfe */
t6    =  6.1005386524e-03f, /* 0x3bc7e707 */
t7    = -3.6845202558e-03f, /* 0xbb7177fe */
t8    =  2.2596477065e-03f, /* 0x3b141699 */
t9    = -1.4034647029e-03f, /* 0xbab7f476 */
t10   =  8.8108185446e-04f, /* 0x3a66f867 */
t11   = -5.3859531181e-04f, /* 0xba0d3085 */
t12   =  3.1563205994e-04f, /* 0x39a57b6b */
t13   = -3.1275415677e-04f, /* 0xb9a3f927 */
t14   =  3.3552918467e-04f, /* 0x39afe9f7 */
u0    = -7.7215664089e-02f, /* 0xbd9e233f */
u1    =  6.3282704353e-01f, /* 0x3f2200f4 */
u2    =  1.4549225569e+00f, /* 0x3fba3ae7 */
u3    =  9.7771751881e-01f, /* 0x3f7a4bb2 */
u4    =  2.2896373272e-01f, /* 0x3e6a7578 */
u5    =  1.3381091878e-02f, /* 0x3c5b3c5e */
v1    =  2.4559779167e+00f, /* 0x401d2ebe */
v2    =  2.1284897327e+00f, /* 0x4008392d */
v3    =  7.6928514242e-01f, /* 0x3f44efdf */
v4    =  1.0422264785e-01f, /* 0x3dd572af */
v5    =  3.2170924824e-03f, /* 0x3b52d5db */
s0    = -7.7215664089e-02f, /* 0xbd9e233f */
s1    =  2.1498242021e-01f, /* 0x3e5c245a */
s2    =  3.2577878237e-01f, /* 0x3ea6cc7a */
s3    =  1.4635047317e-01f, /* 0x3e15dce6 */
s4    =  2.6642270386e-02f, /* 0x3cda40e4 */
s5    =  1.8402845599e-03f, /* 0x3af135b4 */
s6    =  3.1947532989e-05f, /* 0x3805ff67 */
r1    =  1.3920053244e+00f, /* 0x3fb22d3b */
r2    =  7.2193557024e-01f, /* 0x3f38d0c5 */
r3    =  1.7193385959e-01f, /* 0x3e300f6e */
r4    =  1.8645919859e-02f, /* 0x3c98bf54 */
r5    =  7.7794247773e-04f, /* 0x3a4beed6 */
r6    =  7.3266842264e-06f, /* 0x36f5d7bd */
w0    =  4.1893854737e-01f, /* 0x3ed67f1d */
w1    =  8.3333335817e-02f, /* 0x3daaaaab */
w2    = -2.7777778450e-03f, /* 0xbb360b61 */
w3    =  7.9365057172e-04f, /* 0x3a500cfd */
w4    = -5.9518753551e-04f, /* 0xba1c065c */
w5    =  8.3633989561e-04f, /* 0x3a5b3dd2 */
w6    = -1.6309292987e-03f; /* 0xbad5c4e8 */

static const float zero =  0.0000000000e+00f;

static float __sin_pif(float x)
{
    float y, z;
    int32_t n, ix;

    GET_FLOAT_WORD(ix, x);
    ix &= 0x7fffffff;

    if (ix < 0x3e800000) {
        return __sinf(pi * x, zero, 0);
    }

    y = -x;        /* x is assume negative */

    /*
     * argument reduction, make sure inexact flag not raised if input
     * is an integer
     */
    z = floorf(y);

    if (z != y) {                       /* inexact anyway */
        y  *= 0.5f;
        y   = 2.0f * (y - floorf(y));   /* y = |x| mod 2.0 */
        n   = (int32_t)(y * 4.0f);
    } else {
        z = y + two23;                  /* exact */

        GET_FLOAT_WORD(n, z);
        n &= 1;
        y  = n;
        n <<= 2;
    }

    switch (n) {
    case 0:
        y =  __sinf(pi * y, zero, 0);
        break;

    case 1: /* FALLTHRU */
    case 2:
        y =  __cosf(pi * (0.5f - y), zero);
        break;

    case 3: /* FALLTHRU */
    case 4:
        y =  __sinf(pi * (one - y), zero, 0);
        break;

    case 5: /* FALLTHRU */
    case 6:
        y = -__cosf(pi * (y - 1.5f), zero);
        break;

    default:
        y =  __sinf(pi * (y - 2.0f), zero, 0);
        break;
    }

    return -y;
}

float __lgammaf(float x, int *signgamp)
{
    float t, y, z, nadj = 0.0f, p, p1, p2, p3, q, r, w;
    int32_t i, hx, ix;

    GET_FLOAT_WORD(hx, x);

    /* purge off +-inf, NaN, +-0, and negative arguments */
    *signgamp = 1;
    ix = hx & 0x7fffffff;

    if (ix >= 0x7f800000) {
        return x * x;
    }

    if (ix == 0) {
        if(hx < 0) {
            *signgamp = -1;
        }
        return __raise_div_by_zerof(zero);
    }

    if (ix < 0x30800000) { /* |x|<2**-30, return -log(|x|) */
        if (hx < 0) {
            *signgamp = -1;
            return -logf(-x);
        } else {
            return -logf(x);
        }
    }

    if (hx < 0) {
        if (ix >= 0x4b000000) { /* |x|>=2**23, must be -integer */
            return __raise_div_by_zerof(zero);
        }

        t = __sin_pif(x);

        if (t == zero) {
            return __raise_div_by_zerof(zero);    /* -integer */
        }

        nadj = logf(pi / fabsf(t * x));

        if (t < zero) {
            *signgamp = -1;
        }

        x = -x;
    }

    /* purge off 1 and 2 */
    if (ix == 0x3f800000 || ix == 0x40000000) {
        r = 0;
    }
    /* for x < 2.0 */
    else if (ix < 0x40000000) {
        if (ix <= 0x3f666666) {  /* lgamma(x) = lgamma(x+1)-log(x) */
            r = -logf(x);

            if (ix >= 0x3f3b4a20) {
                y = one - x;
                i = 0;
            } else if (ix >= 0x3e6d3308) {
                y = x - (tc - one);
                i = 1;
            } else {
                y = x;
                i = 2;
            }
        } else {
            r = zero;

            if (ix >= 0x3fdda618) {
                y = 2.0f - x;    /* [1.7316,2] */
                i = 0;
            } else if (ix >= 0x3F9da620) {
                y = x - tc;    /* [1.23,1.73] */
                i = 1;
            } else {
                y = x - one;
                i = 2;
            }
        }

        switch (i) {
        default:    /* FALLTHRU */
        case 0:
            z = y * y;
            p1 = a0 + z * (a2 + z * (a4 + z * (a6 + z * (a8 + z * a10))));
            p2 = z * (a1 + z * (a3 + z * (a5 + z * (a7 + z * (a9 + z * a11)))));
            p  = y * p1 + p2;
            r  += (p - 0.5f * y);
            break;

        case 1:
            z = y * y;
            w = z * y;
            p1 = t0 + w * (t3 + w * (t6 + w * (t9 + w * t12))); /* parallel comp */
            p2 = t1 + w * (t4 + w * (t7 + w * (t10 + w * t13)));
            p3 = t2 + w * (t5 + w * (t8 + w * (t11 + w * t14)));
            p  = z * p1 - (tt - w * (p2 + y * p3));
            r += (tf + p);
            break;

        case 2:
            p1 = y * (u0 + y * (u1 + y * (u2 + y * (u3 + y * (u4 + y * u5)))));
            p2 = one + y * (v1 + y * (v2 + y * (v3 + y * (v4 + y * v5))));
            r += (-0.5f * y + p1 / p2);
            break;
        }
    } else if (ix < 0x41000000) {        /* x < 8.0 */
        i = (int32_t)x;
        y = x - (float)i;
        p = y * (s0 + y * (s1 + y * (s2 + y * (s3 + y * (s4 + y * (s5 + y * s6))))));
        q = one + y * (r1 + y * (r2 + y * (r3 + y * (r4 + y * (r5 + y * r6)))));
        r = half * y + p / q;
        z = one;    /* lgamma(1+s) = log(s) + lgamma(s) */

        switch (i) {
        case 7:
            z *= (y + 6.0f);  /* FALLTHRU */

        case 6:
            z *= (y + 5.0f);  /* FALLTHRU */

        case 5:
            z *= (y + 4.0f);  /* FALLTHRU */

        case 4:
            z *= (y + 3.0f);  /* FALLTHRU */

        case 3:
            z *= (y + 2.0f);  /* FALLTHRU */

        default:
            r += logf(z);
            break;
        }

        /* 8.0 <= x < 2**58 */
    } else if (ix < 0x5c800000) {
        t = logf(x);
        z = one / x;
        y = z * z;
        w = w0 + z * (w1 + y * (w2 + y * (w3 + y * (w4 + y * (w5 + y * w6)))));
        r = (x - half) * (t - one) + w;
    } else
        /* 2**58 <= x <= inf */
    {
        r =  x * (logf(x) - one);
    }

    if (hx < 0) {
        r = nadj - r;
    }

    return r;
}
